CC++读写csv文件

C/C++读写csv文件

实现用C++读取.csv文件，并存到STL中
.csv文件即将表格数据转换为用分隔字符分隔的值(也可以不是逗号)

简单的demo

#include 
#include 
#include 

int main(){
    vector<vector<int>> user_arr;
    ifstream fp("xxx/user_data.csv"); //定义声明一个ifstream对象，指定文件路径
    string line;
    getline(fp,line); //跳过列名，第一行不做处理
    while (getline(fp,line)){ //循环读取每行数据
        vector<int> data_line;
        string number;
        istringstream readstr(line); //string数据流化
        //将一行数据按'，'分割
        for(int j = 0;j < 11;j++){ //可根据数据的实际情况取循环获取
            getline(readstr,number,','); //循环读取数据
            data_line.push_back(atoi(number.c_str())); //字符串传int
        }
        user_arr.push_back(data_line); //插入到vector中
    }
    return 0;
}

补充：
将字符串类型数据转换成 int 类型需要先使用 .c_str() 转成 const char* 类型，再用 atoi() 转成 int ，如果转为浮点型则 atof() ，long 型则 atol() 等等。

示例2，csv数据读取

#include 
#include 
#include 
#include 
#include 
 
using namespace std;
 
 
int main()
{
	// 写文件
	ofstream outFile;
	outFile.open("data.csv", ios::out); // 打开模式可省略
	outFile << "name" << ',' << "age" << ',' << "hobby" << endl;
	outFile << "Mike" << ',' << 18 << ',' << "paiting" << endl;
	outFile << "Tom" << ',' << 25 << ',' << "football" << endl;
	outFile << "Jack" << ',' << 21 << ',' << "music" << endl;
	outFile.close();
 
	// 读文件
	ifstream inFile("data.csv", ios::in);
	string lineStr;
	vector<vector<string>> strArray;
	while (getline(inFile, lineStr))
	{
		// 打印整行字符串
		cout << lineStr << endl;
		// 存成二维表结构
		stringstream ss(lineStr);
		string str;
		vector<string> lineArray;
		// 按照逗号分隔
		while (getline(ss, str, ','))
			lineArray.push_back(str);
		strArray.push_back(lineArray);
	}
	
	getchar();
	return 0;
}

示例3 csv数据保存创建文件

#include 
#include 
#include 
#include 
#include 
using namespace std;

void main()
{
    ofstream outFile("Data.csv", ios::out);
    //ios::out：如果没有文件，那么生成空文件；如果有文件，清空文件
    if (!outFile)
    {
        cout << "打开文件失败！" << endl;
        exit(1);
    }
    //写入3行数据
    for (int i = 0; i < 3; i++)
    {
        outFile << 12 << ",";
        outFile << 13 << ",";
        outFile << 14 << ",";
        outFile << "NaN" << endl;
    }
    outFile.close();
    cout << "写入数据完成" << endl;
}

#include 
#include 
#include 
#include 
#include 
#include 

class CSVRow
{
    public:
        std::string const& operator[](std::size_t index) const
        {
            return m_data[index];
        }
        std::size_t size() const
        {
            return m_data.size();
        }
        void readNextRow(std::istream& str)
        {
            std::string         line;
            std::getline(str, line);

            std::stringstream   lineStream(line);
            std::string         cell;

            m_data.clear();
            while(std::getline(lineStream, cell, ','))
            {
                m_data.push_back(cell);
            }
            // This checks for a trailing comma with no data after it.
            if (!lineStream && cell.empty())
            {
                // If there was a trailing comma then add an empty element.
                m_data.push_back("");
            }
        }
    private:
        std::vector<std::string>    m_data;
};

std::istream& operator>>(std::istream& str, CSVRow& data)
{
    data.readNextRow(str);
    return str;
}  
int main()
{
    std::ifstream       file("plop.csv");

    CSVRow              row;
    while(file >> row)
    {
        std::cout <<"4th Element(" << row[3] <<")
";
    }
}